Pumpout stations are used at many docks, and also for recreational vehicles, such as to facilitate pumping out of sewage holding tanks. A typical pump system for such a pumpout station is shown in U.S. Pat. No. 4,854,827 (the disclosure of which is hereby incorporated by reference herein), and various equipment utilizable with such stations is shown in U.S. Pat. No. 5,433,163 (the disclosure of which is also incorporated by reference herein).
Pumpout stations typically use positive displacement pumps, such as reciprocating action diaphragm pumps, to effect pumpout. While such pumps are effective in performing their desired task, they cause the velocity of the fluent material being pumped to constantly change during operation. During the intake stroke of the pump the fluent material which previously left the pump during the discharge stroke slows down. When the pump begins the discharge stroke again, all of the fluent material from the previous stroke now must be pushed further down the line. The fluid on both sides of such pumps (suction and discharge) actually comes to essentially a complete stop each time the pump completes one cycle. This start/stop action creates pressure spikes which are transmitted by the fluent material itself. These pressure spikes not only cause wear on the valves, diaphragm, and drive train, they also dictate the maximum discharge distance and elevation that the pump is capable of reliably achieving. Tests have demonstrated that if the discharge peak pressure is increased the diaphragm and drive train lives life are reduced, and if the discharge peak pressure is high enough the valves will fail.
According to the present invention the problems associated with the prior art pumpout stations, as described above, can be substantially solved by the use of a pulsation dampener. The pulsation dampener greatly decreases the pressure spikes created by a given discharge configuration. Reducing the pressure spikes inherently increases pump reliability, and also allows the pump to pump further and higher while maintaining the same range of pressure peaks. In some installations the addition of a pulsation dampener can eliminate the need for a lift station. In one test of a marine tank pumpout system according to the invention, which had a peak pressure of about 56 psi, an approximately 150 foot horizontal run of 1.5 inch diameter rigid PVC pipe, and a discharge elevation of about eight feet, when a suitable pulsation dampener (according to the invention) is installed the pressure peaks were reduced to about 16 psi.
Pulsation dampeners are well known per se for pumping systems which have problems with pressure spikes. However in modern times pulsation dampeners are almost universally provided with some sort of moving part, which separates the readily compressible gas in the pulsation dampener from the fluent material being pumped. Each time the pump discharges into the chamber of the pulsation dampener the resistance to flow caused by restrictive fittings, long horizontal runs, or elevated discharges causes the fluid level in the pulsation dampener chamber to increase, pressuring the air trapped in the top portion of the chamber. Since it is easier for the pump to compress the air in the chamber than it is to rapidly move the fluent material through the lines, the discharge stroke is essentially distributed over a longer period of time. That is each time the pump completes the discharge stroke and begins an intake stroke the compressed air in the chamber dissipates pushing the fluent material through the outlet of the pulsation dampener, resulting in pressure peaks being reduced for a given installation. Typical prior art systems which utilize a bladder, or some other method of providing moving parts so that air being compressed and the fluent material being pumped are separated in the pulsation dampener, are shown in U.S. Pat. Nos. 5,129,427, 5,199,856, and 1,958,009.
While bladders, or like moving components, can be effective in pulsation dampeners, they are expensive and can wear out, especially if subjected to the type of environment they normally are in a pumpout station. Therefore it is undesirable to use them. However it has been widely felt in the art that if a bladder or like separation mechanism is not used in a pulsation dampener, over time the air charged in the chamber will dissipate into the fluent material being pumped and the pulsation dampener will become flooded. It is for this reason that as a practical matter pulsation dampeners without moving parts are typically not used.
According to the present invention it has been recognized that for marine tank pumpout systems, and similar embodiments, that the problem of flooding of the pulsation dampener chamber does not occur quickly enough to be of any practical significance given the fact that such pumpout systems are normally operated so that different tanks (such as marine holding tanks in ships or boats) are continually being connected to and disconnected from a hose inlet to the pumpout system. It has been found that because of this relatively frequent connection and disconnection each time the pump is turned on the pump pulls air into the system which is caused to pass into the pulsation dampener chamber thereby "recharging" the pulsation dampener. Also near the end of the pumpout of a tank, air will also be pulled into the system, again "recharging" the pulsation dampener. This air-introducing function both at the beginning and the end of each use of the pumpout system means that as a practical matter in marine tank pumpout systems bladderless pulsation dampeners may be utilized without any adverse consequences, resulting in a pulsation dampener that is cheaper and more reliable with more longevity. Pulsation dampeners according to the invention can thus also be configured into very special shapes (which would not be possible or practical if bladders or like moving parts were included) so that a minimum of volume is taken up by the pulsation dampener. As a matter of fact according to the preferred embodiments of the invention a pulsation dampener may be incorporated into a marine tank pump out system without increasing in any way the useful space taken up by the pumpout system, so that existing pumpout systems may be readily retrofit with pulsation dampeners.
According to one aspect of the present invention a marine tank pumpout system is provided comprising the following components: A positive displacement pump having an inlet and an outlet. The inlet and outlet each including at least one check valve. A first connection to the inlet to connect the inlet to a marine tank to be emptied. A pulsation dampener having an inlet connected to the pump outlet and including an open chamber extending upwardly from the pump outlet into which pumped fluent material may flow; the pulsation dampener also including at least one outlet from the chamber; the chamber including no moving parts. And, a second connection from the pulsation dampener to connect the pulsation dampener to a discharge tank or area.
Preferably the pulsation dampener has first and second differently directed outlets, and one of the pulsation dampener outlets is connected to the connection to a discharge area or tank, while the other includes a plug disposed therein. Also typically a check valve from the pump outlet extends into the pulsation dampener inlet to minimize the useful area taken up by the pulsation dampener. The pump typically includes a reciprocating diaphragm pump and the lo pulsation dampener inlet is directly connected to the pump outlet, and typically the pulsation dampener has an interior volume of between about 250-400 cubic inches.
The pulsation dampener may be substantially L-shaped when viewed from the dampener inlet and includes a first portion generally having a substantially parallelepiped configuration and containing the inlet and the outlets, and a second portion generally having a substantially parallelepiped configuration and extending vertically upwardly from the first portion and defining the majority of the chamber. The pump typically includes a motor and the motor and pulsation dampener are positioned with respect to each other so that the motor nests with the pulsation dampener with the motor above the first portion and next to the second portion, so that the system takes up substantially no more useful space with the pulsation dampener than without it. This is important for many docks where the volume for the pumpout system is limited, and to facilitate retrofit of existing installations. In this embodiment the at least one outlet in the first portion typically comprises a first outlet horizontally aligned with the inlet, and a second outlet opening downwardly.
Alternatively the pulsation dampener may be generally C-shaped when viewed from the dampener inlet and includes a first portion having a substantially parallelepiped configuration and containing the inlet and the outlets; a second portion extending vertically upwardly from the first portion and having a bottom area significantly less than a top area of the first portion; and a third portion extending horizontally outwardly from the second portion at a top of the second portion and overhanging the first portion. The second portion may include a side wall overlying the dampener inlet and extending at an angle of between about 30.degree.-60.degree. (e.g. about 45.degree.) to the horizontal back toward the pump. In this case the motor and the pulsation dampener are positioned with respect to each other so that the motor nests with the pulsation dampener with the motor between the first and third portions, and adjacent a second portion, so that--again--the system takes up substantially no more useful space with the pulsation dampener than without it. In this embodiment the first portion at least one outlet typically comprises a first outlet facing downwardly from the first portion, and a second outlet disposed substantially perpendicularly to the inlet, and horizontally directed.
Typically a flexible hose with a releasable connection (as described in U.S. Pat. No. 5,433,163) is provided for connection to a marine tank, and the system is in combination with a marine tank so that the pump withdraws fluent material from the marine tank and pumps it to a discharge tank or area. The marine tank may comprise a holding tank for marine toilet systems, a bilge tank, a liquid product tank on a boat or ship, etc.
According to another aspect of the present invention a pulsation dampener per se is provided comprising: A pulsation dampener casing comprising: an inlet connectable to a pump outlet; an open chamber extending upwardly from the inlet into which pumped fluent material may flow; at least one outlet from the chamber; and the chamber including no moving parts; and wherein the pulsation dampener casing is substantially L-shaped when viewed from the dampener inlet and includes a first portion generally having a substantially parallelepiped configuration and containing the inlet and the outlets, and a second portion generally having a substantially parallelepiped configuration and extending vertically upwardly from the first portion and defining the majority of the chamber.
Typically the at least one outlet in the first portion comprises a first outlet horizontally in line with the inlet, and a second outlet opening downwardly, a plug disposed in one of the outlets. The casing typically comprises 11 gauge stainless steel (e.g. 316L stainless), although less expensive materials such as fiberglass, or even plastic without reinforcing materials, may under some circumstances be suitable. The interior volume of the pulsation dampener is typically between about 250-400 cubic inches.
According to another aspect of the present invention a pulsation dampener is provided comprising: A pulsation dampener casing comprising: an inlet connectable to a pump outlet; an open chamber extending upwardly from the inlet into which pumped fluent material may flow; at least one outlet from the chamber; and the chamber including no moving parts; and wherein the pulsation dampener casing is generally C-shaped when viewed from the dampener inlet and includes a first portion having a substantially parallelepiped configuration and containing the inlet and the outlets; a second portion extending vertically upwardly from the first portion and having a bottom area significantly less than a top area of the first portion; and a third portion extending horizontally outwardly from the second portion at a top of the second portion and overhanging the first portion.
The second portion of the pulsation dampener typically includes a side wall overlying the dampener inlet, and extending at an angle of between about 30.degree.-60.degree. (e.g. about 45.degree.) to the horizontal back over and horizontally past the inlet. The first portion at least one outlet typically comprises a first outlet facing downwardly from the first portion and a second outlet disposed substantially perpendicularly to the inlet, and horizontally directed, with a plug disposed in one of the outlets. The interior volume of the pulsation dampener of this embodiment is substantially the same as for the previous embodiment.
It is the primary object of the present invention to provide a marine tank pumpout system with an effective pulsation dampener, and a pulsation dampener per se, especially one that is easily retrofit to existing pumpout systems and has no moving parts, and takes up substantially no more useful space than if the pulsation dampener is not utilized. This and other objects of the invention will become clear from an inspection of the detailed description of the invention and from the appended claims.